What the Book of Mormon says about Polygamy

And now it came to pass that the people of Nephi, under the reign
of the second king, began to grow hard in their hearts, and indulge themselves somewhat in wicked practices, such as like
unto David of old desiring many wives and concubines, and also Solomon, his son.

[I]f any man espouse a virgin, and desire to espouse another,and the first give her consent, and if he espouse
the second, and they are virgins, and have vowed to no other man, then is he justified; he cannot commit adultery for they
are given unto him; for he cannot commit adultery with that that belongeth unto him and to no one else. And if he have ten
virgins given unto him by this law, he cannot commit adultery, for they belong to him, and they are given unto him; therefore
is he justified.